WDIO31 PGTW 310300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (ASNA) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.6N 65.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 101 NM SOUTHWEST OF KARACHI, PAKISTAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 02A (ASNA) WITH CONVECTIVE BANDING ALONG THE SOUTHERN
SEMICIRCLE OF AN EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC).
CONVECTION IS BEING SUPPRESSED IN THE NORTHERN SEMICIRCLE DUE TO
THE NORTHEASTERLY SHEAR AND DRY AIR IN THAT REGION. ENVIRONMENTAL
ANALYSIS INDICATES THAT 02A IS IN A MARGINALLY FAVORABLE
ENVIRONMENT CHARACTERIZED BY STRONG EQUATORWARD OUTFLOW ALOFT,
MODERATE VERTICAL WIND SHEAR (VWS), THE PRESENCE OF DRY AIR, AND
WARM SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE EXPOSED LLCC SEEN IN THE ANIMATED EIR
IMAGERY. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF AN
EXTENSION OF A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS SATCON: 43 KTS AT 310000Z
   CIMSS ADT: 33 KTS AT 310000Z
   CIMSS AIDT: 37 KTS AT 310000Z
   CIMSS DPRINT: 41 KTS AT 310000Z
   CIMSS DMINT: 39 KTS AT 302059Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE NORTH.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: 02A IS FORECAST TO CONTINUE TRACKING WESTWARD
ALONG THE SOUTHWESTERN PERIPHERY OF THE STR TO THE NORTHEAST
THROUGH TAU 24. AFTER TAU 24, RIDGING TO THE NORTHWEST WILL TAKE
OVER AS THE PRIMARY STEERING INFLUENCE, CAUSING THE SYSTEM TO TRACK
MORE SOUTHWESTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD.
REGARDING INTENSITY, 02A IS FORECAST TO REMAIN IN A MARGINALLY
FAVORABLE ENVIRONMENT DUE TO THE MODERATE VWS AND DRY AIR
ENTRAINMENT. THEREFORE, 02A IS EXPECTED TO MINIMALLY INTENSIFY TO
45 KTS NEAR TAU 12 AS THE CORE FENDS OFF THE DRY AIR AND
EQUATORWARD OUTFLOW CONTINUES TO BE ROBUST. HOWEVER, NEAR TAU 24, A
WEAKENING TREND WILL START AS THE DRY AIR INTRUDES INTO THE CORE OF
THE SYSTEM AND INCREASING VWS COLLECTIVELY ERODES THE SYSTEM.
WEAKENING TO TROPICAL DEPRESSION STRENGTH IS EXPECTED TO OCCUR NEAR
TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN GOOD
AGREEMENT ON A SOUTHWESTWARD BEND AFTER TAU 24. THERE IS A SLIGHT
VARIANCE ON THE DEGREE OF THE TURN THOUGH, RANGING FROM
WEST-SOUTHWEST (NAVGEM) TO SOUTH-SOUTHWEST (GALWEM). THE
CROSS-TRACK SPREAD BETWEEN THESE EXTREMES IS AROUND 150 NM AT TAU
48. TAKING THIS INTO ACCOUNT, THERE IS MEDIUM CONFIDENCE IN THE
JTWC TRACK FORECAST. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT
OVERALL, WITH THE VAST MAJORITY OF GUIDANCE DEPICTING A WEAKENING
TREND AFTER TAU 24. THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO
CONSENSUS WITH HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH//
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